When castable refractory material is used for the construction of furnace wall structures to separate the combustion chamber or heated gasses from the metal structural members or tubes of the wall, relative movement is caused by the difference in thermal expansion between the metal members, plates or tubes of the wall, which may be of carbon steel, and the castable refractory material, which may, for example, be "MOLDIT D", a product of C-E Refractories, a unit of Combustion Engineering, Inc., the assignee of the present application.
Carbon steel, from which the structural members of the tube wall may be made, has a mean coefficient of thermal expansion of 7 to 8.times.10.sup.-6 per degree F. (12.6 to 14.3.times.10.sup.-6 per degree C.), for example, in a typical service range of from 500.degree. to 1000.degree. F. In a similar range of temperatures, "MOLDIT D" has a mean coefficient of thermal expansion of approximately 3.times.10.sup.-6 per degree F. (5.4.times.10.sup.-6 per degree C.). This is with a recommended bulk density, cured and dried, of 124 pounds per cubic foot. "MOLDIT D" has a nominal chemical analysis (calcined basis) of percent by weight as follows:
Al.sub.2 O.sub.3 --45.0 PA2 SiO.sub.2 --36.9 PA2 CaO--13.0 PA2 Fe.sub.2 O.sub.3 --1.5 PA2 FeO--2.2 PA2 TiO.sub.2 --1.1
It is a representative castable material of the type used on furnace walls.
The present invention is designed to accommodate the movement between the metal members of the furnace wall and the cast refractory material. A previous attempt to accommodate this movement is disclosed in U.S. Pat. No. 3,019,561 to Weber. The novel means for accomplishing this accommodation of the relative movement has been devised upon a realization that a free bending force acting on an elongated anchor member will permit the relative motion with a minimum of damage, if any, to the refractory material. Heretofore, such relative motion has created a damaging shear force between the anchors and the metal structural members which tends to destroy the joint between the anchor and the metal member, break the anchor and damage the castable refractory material.